1. Field of the Invention
This application discloses an aluminum alloy cylinder head for an engine having a valve stem guide bore with integral wear surfaces of a different metal alloy to form spaced wear surfaces positioned at opposite end portions of the guide bore.
2. Description of the Related Art
In a conventional aluminum cylinder head, a tubular metal valve guide or sleeve is press fitted into a bore in the aluminum cylinder head. Without this separate valve guide, a rubbing stem portion of a valve quickly wears away at the soft aluminum or aluminum alloy of the cylinder head. This resultants in sloppy and non-axial valve movements and also the passage of relatively large quantities of lubricating oil to the engine combustion chamber by travel between the valve stem and the cylinder head.
The U.S. Pat. No. 4,723,518 to Kawasaki et al. discloses an aluminum alloy cylinder head having hardened valve seats formed by a adding a layer of a copper based alloy on the aluminum alloy. It also discloses the use of a laser beam to melt and fuse copper based alloy applied to the cylinder head in powder metal form.